The carcasses were found on the Beaver Wood Bison Ranch, a herd that’s made its home on reclaimed land on the Mildred Lake oilsands site for more than 20 years. Syncrude has closed the area where an average of about 300 bison and usually up to five workers on the ranch.

Company spokesman Leithan Slade told the Edmonton Journal, “We recognize the possibility of more deaths due to the nature of the disease and the confirmation of these three cases.”

The US CDC says anthrax is a serious infectious disease caused by gram-positive, rod-shaped bacteria known as Bacillus anthracis. Anthrax can be found naturally in soil and commonly affects domestic and wild animals around the world. Although it is rare, people can get sick with anthrax if they come in contact with infected animals or contaminated animal products.

Contact with anthrax can cause severe illness in both humans and animals. Anthrax is not contagious person to person.

Robert Herriman is a microbiologist and the Editor-in-Chief of Outbreak News Today